...preheating the area with a heat gun, and radiating out from the work-site makes the process go much better, if you don't preheat the work area, when you put the solder tip on the board the cold board is acting like a heat-sink and drawing the heat from the work area.
be mindful of the melting temperature of any components associated with the use of the heatgun...a good hair-dryer will work in the absence of an industrial heatgun...also try adding fresh solder to the connection after you preheated the board before wicking the solder, degradation of the properties in the old solder prevents it from wicking properly as well